This invention relates to clamps for clamping telescopically extendable rods relative to concentric tubular members from which the rods extend, and more particularly to a clamping device that selectively permits (1) telescopic extension of the extendable rod from the tubular member while simultaneously preventing rotation of the telescoping rod relative to the tubular member, (2) rotation of the telescoping rod relative to the tubular member while simultaneously preventing linear extension of the rod relative to the tubular member, or (3) selectively locks both the rotation and extension of the telescoping rod relative to the tubular member.
In order to maintain the linear adjustment of telescoping rods relative to the tubular members, circular compression collars having tapered threads have been utilized to compress split end sections of the tubular members against the telescopically extendable rod so that the friction force between the rod and slip end sections retains the rod in linear adjustment relative to the tubular member. This friction force between the two members additionally prevents the rod from rotating relative to the tubular member. This type of clamping device is suitable for most telescoping rod applications.
It becomes necessary at times, however, to adjust the linear extension of the telescoping rod relative to the tubular member while maintaining the rotational alignment of the two members constant (i.e., preventing rotation of the tube members during telescopic adjustment). Additionally, it is occasionally desirable to maintain the telescopic extension constant while permitting the extendable rod to rotate relative to the tubular member from one position to another. It is sometimes necessary to make these extension or rotation adjustments with one hand. Conventional tapered thread type telescopic extension clamps are incapable of permitting single handed adjustment, in that two hands are necessary to hold the tubular member while rotating the compression collar in either direction.
Accordingly, it is desirable to provide a clamping device for telescoping rod members which selectively permits (1) linear telescopic extension of the extension rod relative to the tubular portion while preventing rotation of the rod relative to the tubular member, and (2) rotation of the rod relative to the tubular member while preventing linear extension of the rod relative to the tubular member.